1. Field of the Invention
The present invention relates to a navigation apparatus mounted such as might be on a vehicle, such as an automobile or the like, so as to obtain and display information as to a traveling route and the location of the vehicle, and more particularly to a navigation apparatus for a vehicle, which facilitates correction of errors caused and accumulated by the vehicle location setting either initially or as the vehicle travels.
2. Description of the Prior Art
A conventional navigation apparatus for a vehicle is generally disclosed in Japanese Patent Laid-Open No. 59-204081 (1984) or Japanese Patent Laid-Open No. 58-178214 (1983). The system of latter is provided with a distance detector for detecting a traveling distance of a vehicle, an azimuth, detector for detecting a present traveling direction of the same, and an indicator for indicating the present location of the same, so that the present location of the vehicle is recognized by spherical coordinates or rectangular coordinates and computed as the vehicle travels, thereby being update-displayed.
Besides this, a technique utilizing an artificial satellite (for example, "Cathode-Ray Tube Information Center with Automotive Navigation", SAE Technical Paper Series 840313 by Ford Motor Co.), a system for utilizing a guide system via an arterial road mainly for distance information, and an indication system for a destination in an urban area for obtaining the distance and azimuth information (for example, "On-Board Computer System for Navigation, Orientation and Route Optimization" SAE Technical Paper Series 840485 by Daimler-Benz AG) are well-known.
It is difficult for the aforesaid conventional navigation apparatus for a vehicle to completely eliminate measurement errors in the traveling distance detector and the azimuth detector and computation error in computing the present location. These errors are accumulated with travelling of the vehicle so that an error between the actual location and the indicated position of the vehicle tends to increase. Hence, this kind of navigation apparatus for the vehicle requires relatively frequent error corrections, but the conventional apparatus requires much labor to reset the present location at every correction by means of inputting coordinates of longitude and latitude or inputting coordinates showing relative location with respect to a certain reference point. Therefore, it takes much labor and time to correct the present location, which is very troublesome for a user.